相关疑难解决方法(0)

Hibernate在SessionFactory创建期间抛出此异常:

org.hibernate.loader.MultipleBagFetchException:无法同时获取多个行李

这是我的测试用例:

Parent.java

@Entity
public Parent {

 @Id
 @GeneratedValue(strategy=GenerationType.IDENTITY)
 private Long id;

 @OneToMany(mappedBy="parent", fetch=FetchType.EAGER)
 // @IndexColumn(name="INDEX_COL") if I had this the problem solve but I retrieve more children than I have, one child is null.
 private List<Child> children;

}

Child.java

@Entity
public Child {

 @Id
 @GeneratedValue(strategy=GenerationType.IDENTITY)
 private Long id;

 @ManyToOne
 private Parent parent;

}

这个问题怎么样？我能做什么？

编辑

好吧,我遇到的问题是另一个"父"实体在我父母的内部,我的真实行为是这样的:

Parent.java

@Entity
public Parent {

 @Id
 @GeneratedValue(strategy=GenerationType.IDENTITY)
 private Long id;

 @ManyToOne
 private AntoherParent anotherParent;

 @OneToMany(mappedBy="parent", fetch=FetchType.EAGER)
 private List<Child> children;

}

AnotherParent.java

@Entity …

问题是我的实体中有两个袋子,我想在我的jsf前端显示(后面的Spring,所以没有延迟加载).所以我必须急切地获取它们以在这样的列表中显示信息:

• 第1点(标签1,标签2)(标签1 ...标签n)
• 第2点(标签3,标签4)(标签1 ...标签n)

将两个列表都置于渴望之中并不起作用.所以我尝试了一下fetch join.它允许我获取一个列表,但是当我添加第二个列表时,我得到了已知的"无法获取多个包"错误.

Hibernate可以在查询中处理两个fetch连接吗？

public class PointOfInterest
 @OneToMany(mappedBy="poi")
private List<PointOfInterestLabel> labels = new ArrayList<PointOfInterestLabel>();

@ManyToMany
private List<Tag> tags = new ArrayList<Tag>();

我的获取加入:

SELECT DISTINCT p from PointOfInterest p 
        left join fetch p.labels 
        left join fetch p.tags WHERE p.figure = :figure

在启动时,我的hibernate工厂的创建失败了:

Caused by: org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags
    at org.hibernate.loader.BasicLoader.postInstantiate(BasicLoader.java:94)
    at org.hibernate.loader.hql.QueryLoader.<init>(QueryLoader.java:123)
    at org.hibernate.hql.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:206)
    at org.hibernate.hql.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136)
    at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:101)
    at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:80)
    at org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:98)
    at org.hibernate.impl.SessionFactoryImpl.checkNamedQueries(SessionFactoryImpl.java:557)
    at org.hibernate.impl.SessionFactoryImpl.<init>(SessionFactoryImpl.java:422)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1385)
    at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:954)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:883)
    ... 55 more